title: Communication: IR spectroscopy of neutral transition metal clusters through thermionic emission.
abstract: The resonant multiple photon excitation of neutral niobium clusters using tunable infrared (IR) radiation leads to thermionic emission. By measuring the mass-resolved ionization yield as a function of IR wavenumber species selective IR spectra are obtained for Nb(n) (n = 5-20) over the 200-350 cm(-1) spectral range. The IR resonance-enhanced multiple photon ionization spectra obtained this way are in good agreement with those measured using IR photodissociation of neutral Nb(n)-Ar clusters. An investigation of the factors determining the applicability of this technique identifies the internal energy threshold towards thermionic emission in combination with a minimum required photon flux that rapidly grows as a function of excitation wavelength.
authors.affiliation: FOM Institute for Plasma Physics Rijnhuizen, Edisonbaan 14, NL-3439 MN Nieuwegein, The Netherlands.
authors.forename: Vivike J F
authors.initials: VJ
authors.lastname: Lapoutre
authors.forename: Marko
authors.initials: M
authors.lastname: Haertelt
authors.forename: Gerard
authors.initials: G
authors.lastname: Meijer
authors.forename: André
authors.initials: A
authors.lastname: Fielicke
authors.forename: Joost M
authors.initials: JM
authors.lastname: Bakker